Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
3.~ i6
1 BAGKGI~OU~ OF TIIE_INV~NrION
2 The prosent invention Lelates to the contacting of a
3 least two solids and a fluid wherein on~ solid is in a fluidize-
4 stato and the other solid is entrained by the fluidizing medium
which may be reactive or inert. More p~rticularly, the invention
6 relatQs to the retorting and/or gasific~tion of solid
7 carb~naceous materials such as coal, coke, tar sands, shale, etc.
8 In view of the recent rapid increases in the price of
9 crude oil, researchers have rene~ed their efforts to find
alternate sources of energy and hydrocarbons. More particularly,
11 much research has focused on processes for recovering the
12 hydrocarbons vresent in shale or other hydrocarbonaceous
13 c~ntaining solids such as tar sands or _oal. These processes
14 qenerally involve the heating or pyrolysis of the solid
carbonaceous material to boil off or li~uefy the hydrocarbons
16 trapped in the solid. Other processes involve reacting the solid
17 carb~naceous material with steam, for example, to convert the
13 solid carbonaceous material into more readily usable gaseous and
19 liquid hydrocarbons. Still other processes involve the
combustion of the solid carbonaceous materials with an oxygen
21 containing gas to generate heat. Such processes always involve
22 the use of treatment zone, or reaction vessel wherein the solid
23 is h~ted or reacted. The cost of these treatment zones and the
24 accompanying apparatus and means for tr~nsferring reactants and
heat into or from these zones plays an important and frequently
26 dominant part in determining the overall economics of the
27 process. Typically, the type of reactor can be characterized as
28 bein~ either a fluid bed, entrained bed or moving bed.
29 Typical of prior art processes using a moving bed, is
the well-known Lurqi process. Crushed coal is fed into the top
31 of a moving bed gasifier and upflowing steam endothermically
32 reacts with the coal. Combustion Of a portion of the char with
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1 oxygen ~elow the reaction zone supplies th~ required e~dothermic
2 heat of reaction~ The coal has a long residence time in the
3 reactor of about 1 hour.
4 A typical entrained bed process is the well-known
Kopp?rs-Totzek process in which coal is dried and finely
fi pulv~rized and in~ected into a reactor ~long with steam and
7 oxyq~n. ~he coal is rapidly partially combusted, gasified and
entrained by the hot ~ases. ~esidence time of the coal in the
9 reactor is only a few seconds.
Typical of fluid bed processes is the well-known Union
11 Carbide/Battelle coal gasification process. Crushed and dried
12 coal is i~jected near the bottom of a fluidized bed of coal.
13 Heat for the reaction is provided by hot coal-ash agglomerates
14 which drop throuqh the fluidized bed of coal.
The aforementioned processes have many disadvantages.
16 For _xa~ple, in movinq bed processes the solid residence time is
17 long which necessitates either very large reactors or a large
18 number of reactors. In entrained bed processes the residence
19 time of the solid is short but very large quantities of hot gases
must be utilized to rapidly heat the solids. In fluid bed
21 processes the solids flow rate is lower than with enfrained bed
22 proc~sses becauss gas rates must be kept low in order to maintain
23 the solid in the fluidized state.
24 Many of the disadvantages of these prior art processes
are ~voided or overcome by the process of the present invention
26 which involves the countercurrent flow of ~ fluidized solid heat-
27 transf~r material and an entrained solid carbonaceous material.
2B The pro~ess of the present invention is unique in many aspects
29 but particularly with regard to the hiqh throughput of solids per
unit volume of reactor.
31 The use of fluidized beds has long been known in the
32 art and has been wldely used commercially in the fluid catalytic
108~46~
1 crackin~ of hydrocarbons. Nhen a fluid is passed at a sufficient
2 velo-ity upwardly through a subdivided bed of solids, the bed
3 expands and the particles are supported by the drag forces caused
4 by the fluid passing through the interstices among the particles.
The superficial velocity in he vessel at which the fluid begins
6 to support the solids is known as the minimum fluidization
7 velocity and the velocity at which the solid becomes entrained in
fl the fluid is known as the terminal velocitv. Between the minimum
9 flui~ization velocity and the terminal velocity or entrainment
velocity, the bed of solids is in a fluidized state and it
11 exhibits the appearance and some of the characteristics of a
12 boilinq liquid.
13 The characteristics of a fluidized bed have been
14 previiuslY utilized in many processes, for example, in the
catalytic cracking of hydrocarbons. Fluidized beds are
16 particularly advantageous where intimate contact between the
17 fluidized solids or solids and gases is required. secause of the
18 quasi-liguid or boiling-like state of the bed, there is generally
19 a rapid overall circulation of the solids thr'oughout the entire
bsd. This rapid circulation is particularly advantageous in
21 processes where a uniform temperature is 'reguired throughout the
22 bed. However, such a uniform temperature and uniform mixing of
23 soli~s is frequently a disadvantage in processes where it is
24 desired to maintain a temperature gradient in the reactor or
where it is desired to separate or segregate various types of
26 ' soli~s or where it is desired to carry out chemical reactions to
27 high conversions.
28 Gas fluidized beds consist of a dense particulate phase
29 and a bubble phase with bubbles forming at or near the bottom of
the bed. These bubbles generally grow by coalescence as they
31 rise throuqh the bed. Mixing and mass transfer are enhanced when
32 the bubbl'es are small and evenly distributed throughout the bed;
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1(1 ~31~6~
1 however, when too many bubbles coalesce so that large ~ubbles are
2 for~ed, a surqin~ or pounding-like action results, leading to
3 less efficient heat and mass transfer.
4 The problem of surqing or sluqqing in fluidized beds is
not ~ully understood. An article by D. Geldart, P_wde_
6 TQ_hnol_~y, 7 (1973) 285-292, discusses various characteristics
7 of ~luidized beds and indicates that the phenomena of sluggi~g is
8 influenced by +he density of the fluidization gas, the density of
9 the particles and the mean particle size.
Various solutions have been proposed for controlling
11 slugqing in fluidized beds. The use of baffles and other
12 lnternal structural members or obstacles have been suggested, as
13 for example, in u.s. Patent 2,533,026. Internal devices,
14 however, impede top to bottom solids mixing which is usually
desired in most fluidized bed processes, such as in fluid
16 catalytic cracking.
17 U.S. Patent 2,376,564 discloses a process in which a
18 fluidized catalyst is used to catalytic~lly crack an upflowing
19 gase~us hydrocarbon. This patent, furthermore, discloses the use
of q non-fluidized, heat-transfer material such as balls or
21 pellets.
22 U.S. Patent 3,927,996 discloses a process in which
23 pulvsrized coal is carried through a portion of a bed of
24 fluidized char. The fluidized char is introduced into a lower
portion of the gasifier and reacts with steam to produce a
26 synthesis ~as.
27 SUMMARY_OF_THE_INVENTION
28 A process for the ~asification of a solid carbonaceous
29 material which comprises:
(1) introducing into an upper portion of a gasification
31 vess~sl a first solid co~prising a solid heat-transfer material;
32 (2) introducing into a lower portion of said gasification
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1 vess l a second solid comprising a solid carbonaceous material
2 ~herein the physical characteristics of said first ana second
3 solids dif~er such that the supe{ficial velocity of a fluid
4 flowing throu~h said vessel is greater than the minimum
fluidizinq velocity of said first solid in said fluid and less
6 than the terminal velocity of said first s31id in said fluid
7 while the superf~cial velocity of said fluid is grea~er than the
8 terminal velocity of said second solid in said fluid;
9 (3) maintaining substantially countercurrent plug flow of
said first and second solids in said vessel by passing a reactive
11 gaseous fluid uPwardly through said vessel at a rate sufficient
12 to fluidize said first solid and entrain said second solid
13 wher3by said first solid substantially flows do~nwardly through
14 said vessel while said second solid substantially flows upvardly
through said vessel and reacts with said reactive gaseous fluid
16 forming a fluid product and an at least partially gasified solid
17 carbonaceous material;
18 (4) removing from a lower portion of said vessel said heat-
19 transfer material at a temperature substantially different `than
the temperature at which said heat-transfer material was
21 introduced into said vessel; and
22 (S) removing from an upper portion o~ said vessel saia
23 prod~ct fluid and said gasified solid.
24 Also claimed is a process for retorting a solid
carbonaceous material wherein the fluidizing gas is essentially
26 inert rather than reactive. The inert gas may be recycled
27 product gas from the retort.
28 Also claimed is a process for contacting two solids and
29 a fluid in a ~essel.
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1 BRIEP DESCRIPTIQN OF THE DRAWINGS
2 FIG. 1 is a diagrammatic illustration of one preferred
3 confi~uration of the fluidization vessel.
4 PIG. 2 is a schematic process flow diagram illustrating
a praferred embodiment of the invention as it applies to the
6 gasification of coal.
7 FIG. 3 is a schematic process flow diagram illustrating
8 a preferred embodiment of the invention as it applies to the
9 rstortiny of shale.
DETAILED DESCRIPTION OF THE_INVENTION AND PREFE~RED EMBQ~IMENTS
11 The process of the invention is best described by
12 reference to FIG. 1.
13 One embodiment of the invention broadly comprises
14 feedinq via line 1 a solid heat-transfer material into the upper
porti~n of a treatment zone or vessel 3 wherein said solid is
16 maintained in a fluidized state by an upflowing fluidizatioD gas
17 introduced via line ~. A solid carbonaceous material is fed into
18 a lower portion of the vessel via line 5 and is entrained by the
19 upflowing fluidization gas. The heat-transfer material,
substantially flows downward in said vessel while the solid
21 carb~naceous material flows upward. The flow of the two solids
22 is substantially countercurrent and pluq-like in nature due to
23 the Presence in the bed of a packing of material 7. The
24 upflowing carbonaceous solids are intimqtely contacted with the
flui~izing gas and the downflowing heat-transfer material.
26 Upflowing solids and a fluid product are withdrawn from an upper
27 portion of vessel 3 via line 11 while the downfl~wing solid heat
28 transfer material is withdrawn from a lower portion of the vessel
29 3 via line 13.
The heat-transfer material can be utilized either to
31 transfsr heat from or to vessel 3, dependinq on whether the
32 vsss~l is beinq used as a retort or for an endothermic or
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1 exothermic reaction. In general, the introduction and removal
2 temperatures of the heat-transfer material will be substantially
3 different, at least 100F different and preferably 500 to 2000F
4 different.
S If i+ is desired to use the vessel as a retort,then
6 heat-transfer material is introducea at an elevated temperature
7 relative to the introduction temperature of the carbonaceous
8 solids. As the solid carbonaceous material flows upward it is
9 heatsd by contact with the upflowing fluid and the downflowing
heat-transfer material. As the upflowing solids are heated the
11 more volatile constituents of the carbonaceous solid vaporize
12 and/~r liquefy and become entrained in the upflowing stream of
13 qases and solids. ~hen retorting is desired, it is preferable
14 that the fluidizinq qas is essentially inert relative to the
S soli~ carbonaceous material. The inert gas may comprise, for
16 exampls, recycle product gas from the retort. Cooled heat-
17 transfsr material is withdrawn from a lower portion of the vessel
18 via line 13.
19 If it is desired to use the vessel for an endothermic
reaction, such as the reaction of coal with steam, then the heat-
21 transfer material is introduced at an elevated temperature
22 relative to the introduction temperatura of the carbonaceous
23 soli~ A reactive fluidizing gas such as steam is introduced via
24 line 9. The steam and solid carbonaceous material react as the
two ~lov upward in the vessel while the downflowing heat-transfer
26 material provides at least the major portion of the endothermic
27 heat of reaction.
28 The process of the invention can also bs used for an
29 exothermic reaction such as takes place with the combustion of
coal. Cold heat-transfer material is introduced via line 1 and a
31 reactive fluldizinq gas such as oxygen, is introduced via line 9.
32 As the solid carbonaceous material exothermically rea_ts with the
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1 upflowinq solid carbonaceous material, the downflowing heat-
transfer material absorbs thg heat of re~ction an~ the heat-
3 transfer material is removed via line 1~ at an elevated
4 tsmper~ture.
The term "qasification" is used in the present
6 invention to mean any endothermic or exothermic reaction between
7 ~he solid carbonaceous material and the fluidizing gas. The term
8 "retortinq" is used in the present invention to mean a process
9 whersin a solid carbonaceous material is heated to liberate or
driv~ out volatile or liquefiable hydrocarbons. As is apparent-
11 to ~ny person skilled in the art, retorting and gasification can
12 occur consecutively or concurrently. Furthermore, it is apparent
13 that anY hydrocarbons once formed or liberated in the retort or
14 qasification vessel can undergo further re~ctions in the vessel.
Other suitable fluidizing gases, in addition to steam
16 and ~xygen, include air, CO, CO2, H2, methane, ethane and other
17 liqht hydrocarbons, recycled product gas and mixtures of the
18 above. Whether the gas is reactive or inert will of course
19 depend upon the choice of solid carbonaceous material and
particularly the other reaction conditions maintained in the
21 vssssl including temperature, pressure, and residence time. It
22 is furthermore apparent that the fluidizing gas comprises product
23 qas and/or a vaporized portion of the feed material as the gases
24 flow from the bottom of the vessel to the top.
Choice of appropriately classified solids is a critical
26 fsature of the present invention. The physical characteristics
27 of the downflowinq solid must differ from the upflowing solid
28 such that it is not entrained by the fluidizing gas. The
29 physical characteristics of the downflowing solid must, in
qeneral, differ from the physical characteristics of the
31 upflowing solid such that the superficial velocity of the
32 flui~izing qases flo~ing through the vessel is greater than the
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1081~66
1 minimum fluidizing velocity of the downflowing solid and less
2 than the terminal velocity of the downflowing solid, while the
3 superficial velocity of fluidizing gas is greater than the
4 terminal velocity of the upflowing solid. In general, the
soli~'s physical characteristics which will be most important are
6 size, shape, and density.
7 If one considers only size, shape, and density, and
8 assumes no interparticle forces such as electrostatic forces or
9 van ~er Waals' forces, then the downflowing solid must, in
~eneral, differ in size, shape or density from the upflo~ing
11 solid such that the net force exerted on the downflowing solid is
12 greater than the net force exerted on the upflowing solid. By
13 net force it is meant the sum of the gravitatioaal force exerted
14 on the solid, plus the drag force exert~d on thè solid by the
upflowing fluidization gases, plus the buoyancy orce exerted on
16 the solid by said fluidization gas. Preferably~,~the physical
17 characteristics of the two solids are substantially different
18 such th~t the velocity of the upflowing gases can be varied over~
19 a wide range with the downflowing solid maintained in a fluidi~ed
state while the upflowing solid is entrained. '
21 As mentioned above, other forces, such as van'der
22 Waals~ forces, electrostatic forces, surface tension, etc., may"
23 also influence whether two different solids can simultaneously
24 exist in a fluidized and entrained state. The characteristics
and compatability of any two particular solids can always readily
26 be determined on an experimental basis by any p~rson skilled in
27 the art.
28 The downflowing solid heat-transfer materials can be
29 reactive, inert, or comprise a mixture or composite of reactive
and inert materials. Preferably, however, the downflowing solid
31 is in~rt and preferably in the form of granules, balls or
32 pellets.
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~081~;6
A particularly preferred heat-transfer material is sand.
The upflowing solid carbonaceous material can comprise coal, coke,
lignite, shale, tar sands, sawdust, municipal, industrial or agricultural waste
products, etc., or mixtures thereof.
Catalysts can also be mixed with or comprise part of the upflowing
or downflowing solid. Particularly preferred catalysts are those which are
well known in the hydrocarbon processing industry, for example, catalytic crack-
ing catalysts.
As discussed above, the heat-transfer material and the solid carbon-
aceous solid need only differ in physical characteristics such that substantial-
ly all of the heat-transfer material remains in a fluidized state while the
upflowing solid is entrained in the fluidization gas.
An essential feature of the present invention is that the vessel
must contain a packing material or other suitable internals which essentially
maintains plug flow of the upflowing and downflowing solids in the vessel.
As examples of suitable internals other than packing material which
can be used to maintain plug flow, we mention fixed internals such as plates,
baffles, trays, rods, horizontal screens, perforated plates and the like. The
use of such internals is discussed in "Fluidization" by Davidson and Harrison,
Academic Press 1971, Chapter 13 entitled "Fluidized Beds with Internal Baffles."
~aintaining continuous countercurrent plug flow has many advantages
including:
(1) Plug flow provides for much higher conversion levels of carbon-
aceous material in a smaller reactor volume than is obtainable with fluidized
bed reactors with gross top to bottom mixing. In unpacked fluidized beds or
, in stirred tank reactors, the product stream removed from the vessel approxi-
mates the average conditions in the vessel. Thus, in such processes a mix-
, ture of unreacted or partially reacted material is necessarily removed with
the product stream which leads to costly separations, and recycle of unreacted
materials. Plug flow, however, allows one to operate the process of the
present invention on a continuous basis with the residence time being
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1~8~;6
1 variad precisely to control the deqree of vaporization or
2 reaction. Thus, if desired, one can obtain essentially complete
3 reaction or retortinq of the solid carbonaceous material in a
4 sin~l~ Pass of the solid through the treat~ent zone. Thus, one
can ~void many of the costly separation and recycle costs of
6 prior art processes.
7 (2) The effect of countercurrent pluq flow furthermore has
8 a si~nificant advantaqe with reyard to controlling and optimizing
g the heat-transfer and reaction temperatures in the vessel. For
example, with the hot heat-carrying material ent~ring the top of
11 the vessel and the relatively cold carb~naseous material entering
12 the bottom of the reactor, ~ highly desirable thermal gradient is
13 obtainable with the maximum and minimum temperatures at opposite
14 ends of the vessel. As is well known to those in the heat-
transfer art, countercurrent flow generally provides the most
16 efficient means of heat-transfer.
17 Thus, for example, in the retorting of shale, shale is
18 intr~duced in the bottom of the retort where it contacts the
19 downflowing fluid bed of sand. Because the flow of solids is
countorcurrent and plug-flow-like in nature, the spent shale
21 contacts the hottest sand last and the cold entering shale
22 contacts the cold heat-transfer material first. Thus, a large
23 thermal gradient is created from which the degree of retorting
24 can be controlled and which reduces readsorption of shale oil
into the spent shale. If desired, hot partially spent shale and
26 the -old sand can then be introduced into a countercurrent flow
27 combustion type qasification vessel. The combustor is similar to
28 the rotort except that it is fluidized with air or an
29 oxyq~n-containing gas to burn off the fixed carbon from the shale
and transfer heat to the sand. The shale is entrained upward
31 throuqh the downward flowing bed of sand and passes out of the
32 combustor past the incoming cold sand, having transferred its
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1C381~66
1 heat to the sand. Spent shale thus leaves the combined retorting
2 and combustion system at the lowest temperature in the system.
3 Such a combined system provides an extremely thermally efficient
4 proc3ss in that cold shale enters the process and relatively cold
S spent shale leaves the process.
6 (3) Pluq flow furthermore allows one to substantially
7 reduce the size of the reaction vessel since it eliminates the
8 need for a large disengaging zone as is normally required in
9 unpacked fluidized beds. In many unpacked fluidized beds, a
large portion of the volume of the vessel, freguently from 50% to
11 80~, is used as a disengaging zone. Bubbles formed in the fluid
12 bed burst at the top of the bed spoutin~ upward a large amount of
13 matsrlal. A larqe disengaging zone is necessary to allow this
14 material to drop back into the fluid portion of the bed and avoid
carry-over of the solids out of the vessel along with the
16 flui~izinq gas. Since large bubble coalescence is prevented by
17 the ~ackinq matertal, this bursting is essentially eliminated and
18 only a small disengaqing zone is needed.
19 Pluq flow of the solids in the vessel is obtained by
fillinq the vessel with a packing material. By "substantially
21 pluq ~low'l it is meant that there is no top to bottom mixing and
22 only localized back mixing of the solids as they flow through the
23 vessel. As previously discussed, as the degree of top to bottom
24 back mixinq increases, the efficiency of the process decreases.
Therefore, gross back mixing must be avoided in the present
26 process. While gross back mixing must be avoided, highly
27 localized mixing is desirable in that it increases the degree of
28 cont3ctinq between the solids and gases. The degree of back
29 mixinq is, of course, dependent on many factors, particularly the
bed depth and the size of packing material. In general, the
31 localized back mixing will be substanti~lly confined to within 2
32 to 4 layers of packing material.
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1081~i6
1 Numerous packing materials known to those skilled in
2 the ~rt include spheres, cylinders and other specially shaped
3 items, etc. Any of these numerous packing materials may produce
4 the desired effect in causing the gross flow to be substantially
plug-like in nature while causin~ hiqhly localized mixing. A
k particularlY preferred packing material which is well known to
7 those skilled in the art is pall rinqs. Pall rings are, in
8 gPneral, cylindrical in shape with a portion of the wall of the
9 cvlinder beinq projected inward, which promotes localized
circulation of the solids and gases and which prevents the
11 problem of some solid-wall-type packings in permitting channeling
12 to occur or qravitation of solids or gases toward the reactor
13 wall. Dall rinas are commercially available in nany sizes,
14 including sizes from less than 1 inch in diameter to more than 3
inches in diameter. The choice of size will, of course, depend
16 upon many other factors, such as the bed depth and vessel
17 diameter. These design features and others are, of course,
18 readily determined by any person skilled in the art.
1q A further advantage of the pa^king material and a
critical aspect of the invention depending upon the type of
21 fluidized material is the prevention of slugging in the fluidized
22 bed. In many fluidized beds, the bubbles of fluidized solids
23 tsnd to coalesce much as they do in a boiling liquid. ~hen too
24 many bubbles coalesce, surging or pounding in the bed results,
leadinq to a loss of efficiency in cont~ctinq. Extensive
26 sluqginq occors when enou~h bubbles coalesce to form a single
27 bubble which occupies the entire cross section of the vessel.
28 This bubble then proceeds up the vessel as a slug. The rate and
29 nature of the coalescence of these bubbles is not fully
understood to those skilled in the art but apparently depends on
31 many factors, particularly the height and diameter of the bed and
32 the ParticIes density and the size. One study by Geldart, Po_d__
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~C~81~66
Technology, 7 ~1973) 285-292, characterizes various types of particles
and their tendency for slugging. Geldart characterizes particles as being
either type A, B or C.
Type B particles are characterized in that naturally occurring
bubbles start to form at only slightly above the minimum fluidization
velocity. Type B particles are also characterized in that there is no
evidence of a maximum bubble size and coalescence is the predominant pro-
blem. Sand is a type B solid.
Thus, in the present invention, where sand is the preferred
fluidized solid heat-transfer material, it is critical in order to main-
tain countercurrent plug flow that bubble coalescence be minimized by the
inclusion of a packing material in the bed. Pall rings is the preferred
type of packing material when a type B solid is being fluidized and
particularly when sa*d is fluidized.
Still another important advantage of the packing material and
the downflowing solid is that the reactor volume can be substantially
reduced in size as compared to prior art entrained bed processes because
the packing material and the downflowing solid substantially increases
the upflowing solids hold-up time of the entrained solid. In prior art
- 20 processes involving entrained bed flow, the residence ~ime of the solid
per linear foot of reactor is generally very low. This necessitates
either grinding the reactant solid to a very small size so that it reacts
relatively fast or it requires builting relatively long expensive reactors
in order to increase the total residence time of the solid in the reactor
o~ it requires operating the reactor at a very high temperature in order
to obtain a very fast reaction.
In the process of the present invention, flow of the
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1()~ 66
1 entrained solid carbonaceous material is substantially impeded by
2 the packin~ material. In most cases, depending on the choice of
3 packin~ ma~erial and other factors, the solids hold-up time of
4 the antrained solid is 1-1/2 to 3 times or more greater than with
~ prior art processes operating without a packed bed such as the
6 Kopp~rs-Totzek process. This aspect of the invention is
7 particularly important because in many gasification or retorting
8 processes, the gasification and retorting vessels frequently
9 represent 10~ to 50% of the capital cost of the process. By
doublinq the solids hold-up, one can essentially cut in half the
11 number of reactors needed for the process.
12 Various other embodiments and modifications of the
13 invention are furthermore apparent from FIG. 2 which illustrates
14 a prefarred embodiment of the invention as it applies to the
qasification of a solid carbonaceous material, particularly coal.
16 In FIG. 2, hot sand is fed via line 40 into an upper
17 por~ion of the gasification vessel 42 while coal is fed into a
18 lower ~ortion of the vessel via line 44 by any appropriate means,
19 for example, by a screw feeder. The coal is crushed and sized by
means not shown such that the difference in physical
-21 characteristics, particularly, shape, size and density is such
22 that the coal is capable of being substantially entrained in the
23 flui~ization gas while the heat-transfer material, sand, is
24 fluidized.
The gasifier is filled with a suitable packing material
26 43, preferably pall rings, and the bed of stationary packing
27 material is supported by grid or distributor 50 or other suitable
28 means. Steam or product synthesis gas is fed to the gasifier via
2~ line 52 at a rate sufficient to fluidize the downflowing sand and
entr~in the coal. The downflowing sand loses heat as it flows
31 downward in the vessel and cold sand is removed from the vessel
32 throuqh line 54 and transferred to combustor vessel 65. The coal
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~Cl 81~66
1 endothermically reacts with the steam as it passes upwardly
2 throuqh the qasification vessel 42. The residence time of the
3 coal ~nd the temperature of the reaction zone and other variables
4 can readily be adjusted by one skilled in ~he art to vary the
degree of reaction. The entrained effluents from vessel 42 which
6 can include ash, char, product gas, light hydrocarbons having
7 from 1 to 4 hydrocarbons and higher molecular weight hydrocarbons
8 are removed from the reaction zone via line 56. Preferably, a
9 cycl3ne separator 62 or other suitable separation means is
utilized to separate the solids from the gaseous and liguid
11 products. Separated char is preferably fed to combustor 65 via
12 line 60 and separated gas and any liquid are fed via line 63 to a
13 qas-liquid separator 64 wh~rein the product 63 is separated into
14 a condensable portion 68 and a liqht hy~rocarbon and synthesis
qas portlon 66.
16 The cold sand can be reheated for recycle to the
17 qasifier by any means, but it is preferred to use the process of
18 the present invention to reheat the cold sand by burning char
19 produced in the qasifier 42. Hot char is fed into a lower
portion of combustion vessel 65 and cold sand is introduced into
21 an upper portion of combustor ~ia line 54. Air or some other gas
22 may be used as a lift gas to convey the cold sand from the bottom
23 of qasifier 42 to the top of combustor 65. A combustion gas
24 cont~ining molecular oxygen is introduced into a lower portion of
the -ombustion vessel via line 67 at a rate sufficient to
26 flui~ize the sand and entrain the char. Combustor 65 is
27 preferably filled with a packing materi31 as described
28 previously. The char is combusted as it flows upward heating the
29 sand as it flows downward. The ho`t sand is then conveyed by any
suitable means, for example, by the use of a portion of the
31 product gas, 66, to the top of the gasifier via line 40. Flue
32 qas and ash are removed from the combustor via line 69 and are
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1~81~6~
1 separated, for example, in a cyclone separator 71 into a flue
2 qas 73 and ash 74. The energy in the ho~ flue gas can be
3 recovered and used for power generation or steam generation.
4 Also if aesired, combustor 65 may contain internal coils for
S generatinq steam for any use, but particularly for injection into
6 qasifier 42. One particular advantage of this combination of a
7 flui1ized endothermic gasification combined with a fluidized
eYothermic qasification is the extremely high overall thermal
9 efficiency of the process.
Another advantage and embodiment of the present
11 invantion involves feeding wet coal or a coal-water slurry into
12 the gasification zone. In this case, a relatively inert gas,
13 such as product gas can be used to flui~ize the coal and steam is
14 formed from the water as the coal flows upward through the
~asifler. This embodiment of the invention is particularly
16 advantaqeous since many prior art processes teach that the coal
17 must be dried prior to being fed into the gasifier.
18 Referrinq now to FIG. 3 which describes a preferred
19 embodiment of the invention as it applies to the retorting of a
solid carbonaceous material. FIG. 3 particularly relates to the
21 retorting of shale. Appropriately sized shale is fed into a
22 retorting zone 80 via line 82 from storage 83. Hot sand or some
23 other heat-transfer material is fed into an upper portion of the
24 retorting vessel via line 84. A relatively inert fluidizing gas,
prefsrably recycle gas, is introduced at a lower portion of the
26 rstorting vessel via line 86 at a rate sufficient to fluidize the
27 sand and entrain the shale. The physic~l characteristics,
28 particularly, shape, size or density of the shale and heat-
29 transfer material are sufficiently different, as previously
described, to allow for fluidization of the sand and entrainment
31 of the shale in the fluidizing gas. As the shale passes upward
32 in the retort, it is heated by the downflowing hot sand and at
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1 least a portion or all of the volatile components present in the
2 shale are vaporized or li~uidized. Fluid product and entrained
3 soli~s are removed from the retort via line 85. Hot spent shale
4 or p~rtially spent shale is passed to combustor via line 86 from
hot cyclone separator 90 and the remaining fixed carbon or
6 resi~ual hydrocarbons in said shale are combusted to reheat the
7 cold h~at-transfer material substantially as described with
8 regard to combustor 65 in FIG. 2. The fluid product stream 92
9 from cyclone separator 90 is passed to gas-liquid separation zone
93 wherein shale oil is removed via line 94 and light gases are
11 removed via line 95. A portion of the light gases is recycled
12 via line 86 to the retort to fluidize fresh shale. A portion of
13 the li~ht ~ases can also be used as a lift gas to convey the
14 rsheated sand from the bottom of combustor 91 to the top of the
rstort via line 84.
16 The present invention as it applies to the retorting of
17 soli~ carbonaceous materials, including coal, has many advantages
18 over the prior art in addition to those previously mentioned.
19 Por example, because of the countercurrent plug flow, the
2~ retorted shale contacts the hottest sand last as the retorting
21 takes place. This increases the shale oil yield by preventing
22 the readsorption of shale on the retorted shale.
23 Coal may also be retorted as described in FIG. 3. The
24 present invention lS particularly useful with caking coals
because the high velocity, essentially inert gas and intimate
26 contactinq of the coal with the heat carrier help prevent caking
27 of the coal.
2~ Repressntative reaction conditions for the preferred
29 embodiment of the process illustrated in FIGS. 2 and 3 appear in
Table I. The retorting and reaction conditions in the vessel can
31 vary widely depending on many interrelated factors, including:
32 ths type of the carbonaceous material, the type of heat-transfer
_ 19 _
` 1~8~66
1 material, temperature, pressure, fluidization gas composition and
2 velocity, and the type and size of packinq material. These
3 parameters can readily be adjusted by any person skilled in the
4 art to obtain the desired results.
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10~ 66
1 The foreqoing FIGS. 1-3 have been utilized to
2 illustrate various embodiments of the invention. The present
3 invention, however, may, in general, be adapted to any process
4 reguiring intimate contacting of two or more solids and a fluid.
The fluid may be reactive or inert and be a gas or liquid. The
6 invention will find application in many processes wherein it is
7 desired to effect a physical and/or chemical change in the
8 fluidizing medium or in one or more of the countercurrent flowing
9 soli~s. The Present invention may be readily adapted to many
existing processes wherein fluidization technology is already in
11 use, for example, heat-transfer, heat-treating, solids coating,
12 drying, solids aqqlomeration and attrition; chemical reactions,
13 for ~xample, oxidation, chlorination, nitration, hydrogenation,
14 dehydroqenation, cracking, isomerization, alkylation,
polymerization, etc. The invention will also find application in
16 scrubbing processes and ion exchange. The process of the present
17 invention can readily be adapted to the a.bove-mentioned processes
18 and ~any others b~ any person skilled in the art. Accordingly,
19 th.e invsntion is not to be construed as limited to the specific .-
embodiments or examples discussed but only as defined. in the
21 appendsd claims or substantial equivalents of the claims.
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